Effect of rewarming in oxygenation and respiratory condition after neonatal exposure to moderate therapeutic hypothermia

Abstract

Background: To assess changes in clinical condition and oxygenation in neonates after rewarming following moderate therapeutic hypothermia (MTH) for neonatal encephalopathy. Methods: Retrospective study of 28 neonates receiving MTH in a tertiary neonatal intensive care unit in Israel. We compared pre-and 24 h post-rewarming arterial oxygen saturation (SaO2) as measured by the blood gases analyzer, pulse-oximetry saturation (SpO2), and cardio-respiratory condition. Results: The SpO2 declined from 96.9% (±2.9) before rewarming to 95.2% (±2.6) after rewarming (p < 0.001). Twelve neonates (42.9%) had clinical respiratory impairment (needing higher respiratory support or had new onset desaturations). In 16 neonates (57.1%) with no change in respiratory support after rewarming, SpO2 decreased from 98.3 ± 1.9% to 95.6 ± 3.0% (p < 0.001) and SaO2 decreased from 97.1 ± 1.7% to 96.0 ± 2.3% (p = 0.002). The mean SpO2 decrease was greater than mean SaO2 decrease (2.63 ± 1.8 and 1.1 ± 1.3 respectively, p = 0.021). Conclusion: Neonates who underwent MTH showed reduction in oxygenation after rewarming either by decreasing SpO2 or increasing FiO2 requirements. The SpO2 decline was larger than the SaO2 decline. We suggest careful monitoring of neonates after rewarming. Keywords: Asphyxia, Cooling, Rewarming, Hemoglobin-oxygen dissociation, Neuroprotection